Radio repeater system



Nov. 23 1926.

6 A TTORNE Y Patented Nov. 23, 1926.

UNITED stares Partnr orties.

nn Loss K. MARTIN, or wnsr ORANGE, N'Ewannsnr, AssreNon To Ansmann wenn PHONE AND Tanne-Rari; coivrraNY, A consonancia Yeni-r.

RADIO BEPEATER SYSTEM.

Application tiled March 22, 192

This invention relates to radio signaling systems, and particularly to a method and means for operating a 'system employing one or more repeater stations between the terminal stations thereof, which method is characterized by the changing of the frequencies of the received waves at each repeater station `in accordance with. a. definite plan, whereby singing of individual repeaters orbetween repeater stations or with a terminal station may be prevented, and whereby the number of frequencies per channel does not exceed a predetermined number irrespective of the number of repeater stations.

In the operation of a long distance radio system having one or more repeaters between the terminal stations thereof, it has heretofore been necessary to change each received frequency of each transmission channel' at each repeater to a different frequency; in order to prevent currents transmitted from the same repeater from entering the receivingcircuits thereof or the receiving circuits of other channels at a distant repeater or terminal station.l For a system without repeaters, two vfrequencies are normally required for each two-way channel, one for transmitting' yin one directionl and another for transmitting in the opposite direction. Considering, for the purpose of illustration, a system of the prior art having two terminal stations and a single repeater therebetween, if we transmit from one terminal a frequency f, and from the other a frequency f2, vsinging may be prevented only by changing at-the repeater the frequency', to a third frequency such as f, before radiating it therefrom to the distant terminal to which it is ini tended to go; and similarly, by changing the frequency f2 to a fourth frequencysuch as f, before radiating` it therefrom. l/Vhile singing will thereby be avoided both at the repeater station and lalso with `theterminal stations, it is obvious that this result 'is obtained only by a liberaluse of the frequency spectrum since the system requires four frequencies to effect two-way transmission between terminal stations of a system 'involving only one repeater. If two or more repeaters are included in such a system, the number of frequencies required for the system. will., in general', be increased sensi No. 701,186.

two per channel for each repeater. bviously, the large demand made upon the frequency spectrum by such a system greatly reduces the field of use of radio repeaters. The applicant has found that by the use of means for controlling the direction of transmission and the reception of waves of the various frequencies and means for changing` and selecting the frequencies, it is possible to greatly reduce the number of frequencies required by a multi-'repeater radio system below the number given above, namely two per channel per repeater.

In my co-pendmgapplication, Serial No. 613,460, filed JanuarylS, 1923, I disclose a method and means for operating a radio communication system involving the use of repeaters, in which system the number of frequencies per channel of communication does not exceed two, regardless of the number of repeaters involved. The system disclosed in the said co-op'ending` application is characterized by the reception at any repeater station of waves from both directions of the same frequency and by transmitting` the waves in both directions from the same repeater station at the same frequency, which frequency, however, is different from the reception frequency.

It is the object of the present invention to provide a method and'means for effectingl two-way communication between tworadio stations of a system employing a plurality of repeaters therebetween, the said method being characterized by the reception at any repeater station of waves from both directions at different frequencies and by transmitting from the same station in both directions at different frequencies, the receptiony frequencies constituting, in effect, one side band of a' controllingl carrier frequency and the transmitting frequencies constituting the-other side baud.

The invention willY be clearly understood fromL the following description, when read in connection with the attached drawing, of which Figure l shows schematically one form of embodiment of the invention; Fig. 1tL is a modification of part of Fig. l; Fig. 2 shows directional characteristics of the receiving antennae of a repeater station, and Figs. 3 land 4 are 'frequency charts showing the distribution of the frequencies throughout the/entire" system. 'f

'lli

Fig. l shows primarily the circuit arrangement in schematic forni of one of the repeater stations, as, for example, BH1, and incidentally the West terminal station and also part of the receiving circuit of the adjacent repeater station RRZ. The West station, which may be of any Well-known type, comprises a transmitting antenna Tii1 adapted to transmit, for example, the frequency f2 of Fig. 3. lt may also be designed and adjusted to tiansmit also the frequency f, for controlling the modulation at the various repeater stations. However, it is desirable to point out that a separate transmitting antenna may be used in connection with the system for transmitting the modulating frequency f1. The West station also comprises a receiving antenna RA, which is designed and adjusted for the reeeption of signals coming from the east. It is to be understood that the terms east and West have been chosen arbitrarily to describe this invention and constitute no limitation thereon.

At the radio repeating station RR each of the receiving antennae Ri-, and RA, is designed and adjusted, in Ways well-known to those skilled in the art, for receiving signals efficiently from only one direction. Tt is Well-knoivn that an antenna structure comprising a vertical antenna such as l and a loop such as 2 may have directional characte 1istics such as shown in Fig. 2,-that is to say, by the proper adjustment of the constants of each antenna circuit, and by proper orientation of the loop,.the combined structure may be caused to receive most efficiently from only one direction, as shown in Fig. 2. For example, the antenna RA, may be adjusted to receive most efficiently from the \vest,-that is to say, signals transinitted from the antenna Titi, and the antenna Rit., may in like manner be adjusted to receive` most efficiently from the east,- that is, the frequency transmitted from one of the transmitting antennae associated with the repeater BH2. By means of the condensers 3 and 6, the loops 2 and 5 may be properly tuned. M M2, Ml., and lsf, are modulators in which the received signaling frequencies are beaten With another frequency which may be termed the modulatin-g frequency. This frequency may be received by the antenna R., or supplied by a local oscillator as shoivn in Fig. 1"'. C indicates a controlling device for controlling the modulating frequency f1, and A, is an amplier for producing the required degree of amplification to the frequency f, before impressing it upon the modulating devices. F1, F2, F., and FA1 represent band filters and A1, A2, A, and A, represent amplifiers. The output side of the amplifier n., is connected with the transmitting antenna TA2 by means of which oscillations of the frequency 7"', are transmitted and received by the autenna Riti, of the adjacent repeater station RRZ. The transii'iitting antenna Tir, is in* tended to transmit the oscillations of the frequency to the antenna Riff, associated with the West station. The transmitting u ntennee, such as Tril, T122, Tita, etc., as shown, are not directive in the sense in which the Word directive7 is normally used iii the art, but antenna arrangements to give directive transmission may be used with equal effectiveness in the operation of this system.

Let it be assumed that oscillations of the frequency f, are being transmitted from the antenna TA, or by another antenna of the system and are being received by the antenna R, associated with the repeater station RR, and also by similar antennae of the other repeater stations, or that the oscillations are supplied locally by means of an oscillation generator as in Fig. 1n. These oscillations amplified by A, Will be impressed upon the modulators M, to M4, inclusive. Simultaneous with the reception of the modulating frequency f1, oscillations of the frequency f2 transmitted by TA, Will be received by the antenna RA, and Will thereby be impressed upon the modulator M1. Oscillations of the frequency f2 Will also be impressed upon the antenna RAS, but since this antenna circuit is designed and adjusted to receive efficiently only from the opposite direction, that is, from the east, substantially no current will be impressed thereby upon the modulator M2. The current of the frequency impressed upon the modulator M, will be beaten therein with the frequency f, and the difference frequency will be selected by the filter F1, Which difference frequency, after being ainplied by the amplifier A1, Will be impressed upon the modulator This dif ference frequency will be beaten in the modulator M3 with the frequency f, and the difference frequency Will be selected by the filter F3 and impressed upon the amplifier A3. This frequency designated fr., When amplified, Will be radiated by the antenna TA, and will be received by the antenna BA, of the repeater station Which is designed for efficient reception from the West. Since this may be more clearly understood by assigning specific values to the variousV frequencies, it will be assumed for the purpose of description that the freiin leemte transmitting antenna TA., of repeater station BH2 is transmitting the frequency f4 which will be assumed to be 75() kilocycles. This frequency will be received at station RR1 by the antenna RA3 designed for eiiicient reception from the east and will be beaten in the modulator M2 with the modulating frequency of 650 kilocycles. The difference frequency, namely L00 kilocycles, will be selected by the lter F2 and after amplification by A2', will beV impressed upon the modulator M4. Herein this difference frequency of l0() liilocycles will be beaten with the modulating frequency of G50 kilocycles producing` 750 and v550 lrilocycies. The difference frequency, namely 550 kilocycles, will be selected by the lter F4 and after amplification by A4, will be radiated'by the ann tenna TAS. This frequency, designated on the drawing as f5, will be received by the receiving antenna RA1 of the west station, Which is designed for eiiicient reception from the east, and will be impressed upon receiving apparatus at that station.

Fig. 3 shows that the frequency f2 transmitted from the west station, becomes f3 at the first repeater station and is translated back to f., at the second repeater station, and again translated to f3 at the third repeater station, from which it is received by the east terminal station. In a similar manner, the transmitting frequency f4 from the east station becomes f5 at the third repeater station, thence changing to f4 at the second repeater station and finally becoming f5 at the first repeater station, from which it is transmitted to the west terminal station. It will be seen from'this frequency distribution diagram that at any repeater station the re ceived currents are upon one side of the modulating frequency f1 and the transmitted frequencies from the same repeater station are upon the opposite side of this modulating frequency. By separating the frequencies in. this manner, the transmitted frequencies from any station will not affect the receiving circuits of the same station, and by using direction-controlled receiving antennae at each of the repeating stations and the terminal stations, the transmitted frequencies from any station will not produce singing between the said repeater stations or between a repeating station and a terminal station.

While the means herein disclosed for carrying out this invention is substantially that shown in the co-pending application referred to above, the method of operating the system which constitutes the present invention differs from that described in the co-pending application inthat it consists in receiving at each repeater station Waves of different frequencies and in transmitting therefrom waves of different frequencies. But it is to be noted that both of the received frequencies are within one side band and the transmitted fr-equenciesare also within one side band, which side bands, however, are ,oppoe site.

t desired to clearly set forth that while i rence has been made throughout the deiption of my invention of the use of a single frequency, as, for example, or f3, as representing the transmitted or received fre quencies constituting a transmission channel, it is to be understood that the designation of these channels by single frequency waves il for the purpose of rendering the description'simple and therefore clear, but it is not to be construed as limiting the invention in anyway totransniis'sion or reception upon a single frequency. The transmitted and the received waves of each channel may, of (ourse, be a side band of frequencies produced by the modulation of a carrier frequency by the frequencies within the voice range, such as is done in radio telephony, or by the modulation of a carrier frequency by telegraph frequencies, such as is employed in radio telegraphy.

l.Vhile this invention has been disclosed as embodied in a particular form and arrange nient of parts, it is not so limited but is apable of embodiment in other forms without departing from the spirit and scope of the appended claims.

lihat is claimed is:

l. In a radio repeating system having terminal stations and a plurality of repeater stations located therebetween in which two-way signaling is effected by using at 10U each repeater station a transmitting wave of different frequency from the receiving wave, the method for limiting the number of frequencies used throughout the system for each channel of communication to four regardless of the number of repeaters involved, which consists in receiving by directional selection at each repeater station east and west waves of different frequencies, separately beating each wave with the same carrier frequency, the said carrie-r frequency being so chosen as to change the frequency of one of the said received waves by double the amount by which the other received wave is therein changed, and transmitting both of said waves as thus changed.

2. ln a radio repeating' system i'iaving terminal stations and a plurality of repente er stations located therebetween, in which two-way signaling is effected by using at each repeater station a transmitting` wave of different frequency from the received wave, the method of limiting the number of frequencies used throughout the system for `each channel of communication to four, re-

gardless of the number of repeaters involved, which consists in receiving by unidirectional selection at each repeater station, east and west waves of different frequencies,

changing the frequency of each of the said 130 received Waves, the frequency change 01": one of the receive-d Waves being different from that of the other, und transmitting both of the seid waives as thus changed.

In a radio repeating system having terminal stations and :i plurality of repeater stations located therebetween in which tW0- way signaling is elfe-:ted by using at each repeuter station a transmitting Wave of different 'frequency 'from the receiving Wave, the method for limiting the number of frequencies used throughout the system for each channel of communication to four regardless of the number of repeaters involved, which consists in receiving by directional selection at ezuh repeater station east und West Waves olf different frequencies, separately beating each ot the said Waves with zi third frequency, selecting the difference frequencies produced thereby, separately beating the said difference frequencies With the said third frequency, selecting' the dilerence fie quencies produced thereby, and transinitting the latter selected frequencies.

In testimony whereof I have signed my nume to this specification this 20th day of March, 1924.

DE LOSS K. MARTIN. 

